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Abstract:

An image forming apparatus picks up each one of sheets stacked in a tray,
allows a detecting sensor to detect whether a mark indicating a reusable
sheet is assigned to the picked-up sheet, and cumulates the sheet in
which the mark is not detected by the detecting sensor in a cumulative
unit. The image forming apparatus erases a color of an image forming
material by heating the sheet of which the mark is detected by the
detecting sensor and receives the sheet of which the image forming
material is erased in a sheet cassette. The image forming apparatus forms
an image with the image forming material erasable by applying heat to the
sheet received in the sheet cassette.

Claims:

1. An image forming apparatus comprising: a sheet feeding tray which
holds a sheet; a detecting sensor which determines whether the sheet
taken out from the sheet feeding tray is reusable; a reusable sheet tray
which receives the sheet which is determined to be reusable by the
detecting sensor; an erasing unit which erases an image on the sheet
taken out from the reusable sheet tray; and a printer that prints an
image on the sheet from which the image has been erased by the erasing
unit.

2. The apparatus according to claim 1, wherein the erasing unit erases
the image on the sheet by heating.

3. The apparatus according to claim 2, further comprising: a new sheet
tray which holds a new sheet, wherein the erasing unit does not heat the
sheet and supplies the sheet to the printer, if an image is printed on
the sheet held on the new sheet tray, whereas the erasing unit heats the
sheet and supplies the sheet to the printer, if an image is printed on
the sheet held on the reusable sheet tray.

4. The apparatus according to claim 3, wherein the detecting sensor
detects whether a mark indicating a reusable sheet is assigned to the
sheet in the sheet feeding tray.

5. The apparatus according to claim 4, wherein the printer prints the
mark indicating the reusable sheet on which an erasable image is printed
by the printer.

6. The apparatus according to claim 3, wherein the erasing unit comprises
an endless member to rotate, and a heat source to heat the sheet with an
erasing temperature through the endless member.

7. The apparatus according to claim 6, wherein the endless member is a
belt, in the belt, a location where the heat is supplied from the heat
source and a location where the belt is brought into contact with the
sheet are different from each other, and the belt is driven while
maintaining the heat supplied from the heat source and applies the heat
maintained to the sheet at the location where the belt is brought into
contact with the sheet.

8. The apparatus according to claim 6, wherein the endless member is a
belt, in the belt, a location where the heat is supplied from the heat
source and a location where the belt is brought into contact with the
sheet are the same, and the belt delivers the heat supplied from the heat
source to the sheet.

9. The apparatus according to claim 3, wherein the printer prints an
image on the sheet with ink erasable by the erasing unit.

10. The apparatus according to claim 3, wherein the printer prints an
image on the sheet with toner erasable by the erasing unit.

11. An image forming method comprising: holding a sheet on a sheet
feeding tray; determining whether the sheet taken out from the sheet
feeding tray is reusable; receiving the sheet which is determined to be
reusable on a reusable sheet tray; erasing an image on the sheet taken
out from the reusable sheet tray; and printing an image on the sheet from
which the image has been erased.

12. The method according to claim 11, wherein the image on the sheet is
erased by heating.

13. The method according to claim 12, further comprising: holding a new
sheet on a new sheet tray, supplying the new sheet which is not heated to
a printer, if an image is printed on the sheet held on the new sheet
tray, and supplying the sheet which is heated for erasing to the printer,
if an image is printed on the sheet held on the reusable sheet tray.

14. The method according to claim 13, wherein the determining is
detecting whether a mark indicating a reusable sheet is assigned to the
sheet in the sheet feeding tray.

15. An image forming apparatus comprising: first holding means tray for
holding a sheet; detecting means for determining whether the sheet taken
out from the first holding means is reusable; second holding means for
receiving the sheet which is determined to be reusable by the detecting
means; erasing means for erasing an image on the sheet taken out from the
second holding means; and printing means for printing an image on the
sheet from which the image has been erased by the erasing means.

16. The apparatus according to claim 15, wherein the erasing means erases
the image on the sheet by heating.

17. The apparatus according to claim 16, further comprising: a third
holding means for holding a new sheet, wherein the erasing means does not
heat the sheet and supplies the sheet to the printing means, if an image
is printed on the sheet held on the third holding means, whereas the
erasing means heats the sheet and supplies the sheet to the printing
means, if an image is printed on the sheet held on the second holding
means.

18. The apparatus according to claim 17, wherein the detecting means
detects whether a mark indicating a reusable sheet is assigned to the
sheet in the first holding means.

19. The apparatus according to claim 17, wherein the printing means
prints a mark indicating a reusable sheet on which an erasable image is
printed by printing means.

20. The apparatus according to claim 17, wherein the erasing means
comprises an endless member to rotate and heat means to heat the sheet
with an erasing temperature through the endless member.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a Continuation of application Ser. No.
12/330,972 filed Dec. 9, 2008, which is based upon and claims the benefit
of U.S. Provisional Applications No. 61/013,472, filed Dec. 13, 2007 and
No. 61/013,474, filed Dec. 13, 2007, the entire contents of all of which
are hereby incorporated herein by reference.

TECHNICAL FIELD

[0002] The present invention relates an image forming apparatus capable of
forming an image with an erasable image forming material and an image
erasing apparatus capable of erasing the image formed of the erasable
image forming material.

BACKGROUND

[0003] In the past, examples of a printing method used in printers include
an electrophotographic type, an ink-jet type, a thermal recording type,
and a thermal transfer type. In recent years, in order to reduce burdens
on the environment and an amount of emission of carbon dioxide, there was
suggested a method of reusing sheets used in printers. For example,
JP-A-06-155906 discloses a method of recording images several times using
sheets in which coloring and color-erasing are possible by heating: In
addition, JP-A-11-268409 discloses a method of reusing sheets by erasing
images printed on the sheets with color-erasable toner with heat. In
addition, JP-A-10-88046 discloses a method of reusing sheets by erasing
images printed on the sheets with color-erasable ink with heat.

[0004] On the other hand, in an actual use environment such as offices, in
many cases, sheets on which conventional non-erasable images are printed
(non-reusable sheets) and sheets on which erasable images are printed
(reusable sheets) coexist. In this case, it is necessary to surely
distinguish between the non-reusable sheets and the reusable sheets. For
example, when the non-reusable sheets are erroneously processed as the
reusable sheets, there is a high possibility that other images are
printed on the non-reusable sheets with the images on the non-reusable
sheets being not erased. Since the plurality of images are printed on the
sheet in an overlapped manner in this case, the sheet cannot be used as a
document. That is, in the actual use environment such as offices, a high
possibility that the non-reusable sheets and the reusable sheets coexist
has to be taken into consideration.

[0005] At present, a method of erasing an image on a sheet by heating is
generally used as a sheet reusing method. In this method, an image
erasing mechanism includes a heat roller and a thermal bar. In the image
erasing mechanism, in order to immediately supply heat to be used to
erase an image on the reusable sheet supplied by a user, residual heating
is generally necessary. In this case, much energy is unnecessarily
consumed. Moreover, since a thermal head scrapes the surface of a sheet,
it is considered that considerable deterioration in an erase performance
occurs due to attachment of toner or ink to the thermal head.

SUMMARY

[0006] An object of the invention is to provide an image forming apparatus
capable of preventing erroneous use of reusable sheets. Another object of
the invention is to provide an image erasing apparatus capable of
reducing deterioration in a performance with low power consumption.

[0007] According to an aspect of the invention, an image forming apparatus
includes: a tray in which sheets are stacked; a detecting sensor which
detects whether a mark indicating a reusable sheet is assigned to the
sheets; a cumulative unit which cumulates the sheets of which the mark is
not detected by the detecting sensor; a color erasing unit which erases a
color of an image forming material attached onto the sheets of which the
mark is detected by the detecting sensor; a sheet cassette which receives
the sheets of which the image forming material is erased by the color
erasing unit; and an image forming unit which forms an image by attaching
the image forming material onto the sheets received in the sheet
cassette.

[0008] According to another aspect of the invention, an image forming
apparatus includes: a tray in which sheets are stacked; a detecting
sensor which detects whether a mark indicating a reusable sheet is
assigned to the sheets; a cumulative unit which cumulates the sheets of
which the mark is not detected by the detecting sensor; a sheet cassette
which receives the sheets of which the mark is detected by the detecting
sensor; a color erasing unit which erases a color of an erasable image
forming material attached onto the sheets taken out from the sheet
cassette; and an image forming unit which forms an image by attaching the
image forming material onto the sheets of which the image forming
material is erased by the color erasing unit.

[0009] According to still another aspect of the invention, an image
erasing apparatus includes: a heat source which heats a sheet on which an
image is formed with an image forming material erasable by heating; a
belt which applies heat supplied from the heat source to the sheet being
brought into contact with the belt while being transported; and a sheet
cassette which receives the sheet to which the heat supplied from the
heat source is applied through the belt.

[0010] Additional objects and advantages of the invention will be set
forth in the description which follows, and in part will be obvious from
the description, or may be learned by practice of the invention. The
objects and advantages of the invention may be realized and obtained by
means of the instrumentalities and combinations particularly pointed out
hereinafter.

DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawing, which are incorporated in and constitute
a part of the specification, illustrate embodiments of the invention, and
together with the general description given above and the detailed
description of the embodiments given below, serve to explain the
principles of the invention.

[0012] FIG. 1 is a diagram illustrating a first configuration example of
an image forming apparatus.

[0013] FIG. 2 is a diagram illustrating the first configuration example of
the image forming apparatus.

[0014] FIG. 3 is a flowchart explaining an operation example of a reuse
processing unit.

[0015] FIG. 4 is a diagram illustrating a second configuration example of
the image forming apparatus.

[0016] FIG. 5 is a diagram illustrating the second configuration example
of the image forming apparatus.

[0017] FIG. 6 is a diagram illustrating a third configuration example of
the image forming apparatus.

[0018] FIG. 7 is a diagram illustrating the third configuration example of
the image forming apparatus.

[0019] FIG. 8 is a diagram illustrating a fourth configuration example of
the image forming apparatus.

[0020] FIG. 9 is a diagram illustrating the fourth configuration example
of the image forming apparatus.

[0021] FIG. 10 is a flowchart for explaining an operation example of a
printer of the image forming apparatus having the fourth configuration
example.

[0022] FIG. 11 is a flowchart for explaining an operation example of the
reuse processing unit of the image forming apparatus having the fourth
configuration example.

[0023] FIG. 12 is a diagram illustrating a configuration example of an
image forming apparatus capable of printing a mark with special ink.

[0024] FIG. 13 is a diagram illustrating a first configuration example of
an erasing mechanism.

[0025] FIG. 14 is a diagram illustrating a configuration example of a belt
used in the erasing mechanism shown in FIG. 13.

[0026] FIG. 15 is a diagram illustrating a second configuration example of
the erasing mechanism.

[0027] FIG. 16 is a diagram illustrating a configuration example of a belt
used in the erasing mechanism shown in FIG. 15.

DETAILED DESCRIPTION

[0028] Hereinafter, an embodiment of the invention will be described in
detail with reference to the accompanying diagrams.

[0029] First, a first configuration example of an image forming apparatus
will be described according to the embodiment.

[0031] The sheet cassette 10 is a cassette which receives sheets. The
sheet cassette 10 stores printing sheets P on which an image is printed
by the printer 12A. The cumulative unit 11 cumulates sheets which are not
reused. The printer 12A forms an image on each sheet P. In the first
configuration example shown in FIGS. 1 and 2, the printer 12A is an
ink-jet type printer. The printer 12A is a color printer. The sheet
discharging tray 14 holds the sheets printed by the printer 12A.

[0032] The sheet feeding tray 16 is a sheet holding unit which holds
sheets which are a target processed by the reuse processing unit 18.
Reusable sheets and non-reusable sheets may be stacked together in the
sheet feeding tray 16. In this case, a user may stack printed sheets in
the sheet feeding tray 16 without considering whether the printed sheets
are the reusable sheets or the non-reusable sheets. The reuse processing
unit 18 distinguishes between the reusable sheets and the non-reusable
sheets. The reuse processing unit 18 also functions as erasing an image
printed on the reusable sheets. In this case, the reuse processing unit
18 functions as an image erasing apparatus.

[0033] Next, the configuration of the printer 12A will be described in
detail.

[0034] As shown in FIGS. 1 and 2, the printer 12A includes a sheet feeding
roller 102, a pair of transport rollers 103, a pair of resist rollers
104, a driven roller 105, a driving roller 106, a transport belt 107, a
pressing roller 108, a group of ink-jet heads 109 (109Y, 109M, 109C, and
109Bk), and a pair of transport rollers 110.

[0035] The sheet feeding roller 102 takes out each one of the sheets P
stacked in the sheet cassette 10. The sheet feeding roller 102 feeds the
sheet P taken out from the sheet cassette 10 to the pair of transport
rollers 103 and the pair of resist rollers 104. The pair of resist
rollers 104 transports the sheet P to the transport belt 107 at
predetermined timing. A tension force exerted by the driving roller 106
and the driven roller 105 is applied to the transport belt 107. The
transport belt 107 is driven with rotation of the driving roller 106. The
pressing roller 108 presses the sheet P against the transport belt 107.

[0036] In the transport belt 107, holes are formed at a predetermined
interval on the surface thereof. A negative pressure chamber (not shown)
connected to a fan (not shown) adsorbing the sheet P to the transport
belt 107 is provided inside the transport belt 107. The sheet P is
transported while being adsorbed to the transport belt 107.

[0037] The group of ink-jet heads 109 includes an ink-jet head 109Y, an
ink-jet head 109M, an ink-jet head 109C, and an ink-jet head 109Bk. The
ink-jet heads 109Y, 109M, 109C, and 109Bk are sequentially arranged along
the transport belt 107. For example, in the example illustrating in FIGS.
1 and 2, the ink-jet heads 109Y, 109M, 109C, and 109Bk are sequentially
arranged from an upstream side in a transport direction of the sheet P
transported by the transport belt 107.

[0038] The ink-jet head 109Y is an ink-jet head which ejects erasable
yellow (Y) ink. The ink-jet head 109M is an ink-jet head which ejects
erasable magenta (M) ink. The ink-jet head 109C is an ink-jet head which
ejects erasable cyan (C) ink. The ink-jet head 109Bk is an ink-jet head
which ejects erasable black (Bk) ink.

[0039] The ink-jet heads 109Y, 109M, 109C, and 109Bk form images of
respective colors on the sheet. The ink-jet heads 109Y, 109M, and 109C
eject ink corresponding to a yellow component, a magenta component, and a
cyan component for the respective color images, respectively. The group
of ink-jet heads 109 forms a color image on the sheet by repeatedly
printing the respective color images on the sheet.

[0040] The pair of transport rollers 110 discharges the sheet on which the
image is printed by the group of ink-jet heads 109 to the sheet
discharging tray 14.

[0041] The printer 12A uses the above-described erasable ink to print the
image on the sheet and also print information indicating a reusable
sheet. The information indicating the reusable sheet is information which
is detected by a detecting sensor 123 described below. For example, the
information indicating the reusable sheet is a mark printed on the sheet
under a specific condition. In this case, the printer 12A prints the mark
on the sheet whenever the printer 12A prints an image on the sheet.
Alternatively, this mark may be assigned in advance to the sheet. In this
case, the printer 12A may not print the mark.

[0042] Next, an image forming material used in the printer 12A will be
described.

[0043] The printer 12A uses ink (color-erasable ink) which is the image
forming material capable of being erased by heating with a predetermined
temperature. The ink used in the printer 12A is not limited to a specific
material, but may be ink which is capable of being erased by the heating
with the predetermined temperature. In addition, the image forming
material capable of being used in the ink in the printer 12A is disclosed
in JP-A-2007-212613, JP-A-2007-90704, and Japanese Patent No. 3711017,
for example.

[0044] For example, a basic component of the image forming material such
as color-erasable ink or color-erasable toner is formed of a coloring
compound, developer, binder resin, etc. Since in this image forming
material, a coloring compound is in a colored state under an influence of
the developer, a user is able to recognize colors. In addition, upon
applying heat to the image forming material being in the colored state,
the binder resin is softened. The developer is mainly easy to move to the
surface of the binder resin from inside thereof and easy to move and
diffuse to a sheet. For that reason, since the coloring compound is not
under the influence of the developer, the coloring compound is subjected
to color erasing. Accordingly, colors cannot be recognized as the image
forming material.

[0045] The coloring compound is a precursor compound of pigments which
form coloring images such as characters or figures. It is preferable that
the coloring compound is formed of an electron-supplying organic matter
such as leuco-auramines, diaryl phthalides, polyaryl carbinols, acyl
auramines, aryl auramines, Rhodamine B lactams, indolines, spiropyrans,
or fluorans.

[0047] The binder resin serves as diffusing the coloring compound and the
developer to exhibit colors. On the other hand, the binder resin is
compatible with the coloring compound in heating and does not have
affinity with the developer.

[0048] A printer forming an image with ink as the image forming material
capable of being erased (color-erased) by heating has to be designed so
that a temperature equal to or higher than an erasing temperature is not
applied to the ink in printing. When a temperature within the printer is
raised equal to or higher than the erasing temperature, the color of ink
may be erased before the ink is printed to the sheet. In this case, of
course, a normal image is not formed on the sheet. Moreover, it is
preferable that the erasing temperature of the ink is set as low as
possible in consideration of power consumption of the printer.
Accordingly, the printer needs to be designed so that the temperature
applied to the ink is not high as much as possible.

[0049] In consideration of the above description, an ink-jet type printer
needs to be designed so that the temperature equal to or higher than the
erasing temperature is not applied to the ink therein. For example, it is
preferable that the ink-jet type printer uses a piezo-type printing head
as an ink-jet head. Moreover, a heat dissipation plate (not shown) may be
provided in the vicinity of the head. It is assumed that the ink-jet type
printer shown in FIGS. 1 and 2 (or FIGS. 6, 7, 8, 9, and 12) uses the
piezo-type printing head equipped with the heat dissipation plate. For
example, when the erasing temperature of ink is designed to be
70°, the ink-jet type printer is designed so that the temperature
of ink in the head is surely not 60° or more. This design can be
easily achieved by providing the heat dissipation plate or the like in
the piezo-type printing head.

[0050] Next, the reuse processing unit 18 will be described.

[0051] The reuse processing unit 18 distinguishes the sheets stacked in
the sheet feeding tray 16 as the reusable sheets or the non-reusable
sheets. The reuse processing unit 18 functions as erasing an image
printed on the reusable sheets as well. That is, the reuse processing
unit 18 makes the sheets, on which an erasable image is printed (the
reusable sheets), reusable. The user stacks sheets (at this time, the
reusable sheets and the non-reusable sheets may coexist) in the sheet
feeding tray 16 to be subjected to reuse-processing by the reuse
processing unit 18. A sensor (not shown) detecting the sheets stacked in
the sheet feeding tray 16 detects whether the sheets are placed in the
sheet feeding tray 16.

[0052] In this embodiment, as a sheet holding unit which holds the sheets
as a target of the reuse processing, the sheet feeding tray 16 which
stacks the sheets will be described. However, as the sheet holding unit
which holds the sheets, the invention is not limited to the sheet feeding
tray 16 in which the sheets are stacked. For example, as the sheet
holding unit, a unit capable of receiving a plurality of sheets to be
erected vertically may be used.

[0054] The pickup roller 121 picks up each one of the sheets stacked in
the sheet feeding tray 16 to insert the sheet into the reuse processing
unit 18. For example, when the sensor of the sheet feeding tray 16
detects the sheet, the pickup roller 121 picks up each one of the sheets
stacked in the sheet feeding tray 16.

[0055] The pickup roller 121 inserts the picked-up sheet into the reuse
processing unit 18. The pair of transport rollers 122 transports each of
the sheets supplied by the pickup roller 121 to the detecting sensor 123.
The detecting sensor 123 determines whether the sheet is the reusable
(image erasable) sheet or the non-reusable (image non-erasable) sheet.
The detecting sensor 123 detects information indicating whether the sheet
is reusable or not. For example, the detecting sensor 123 detects whether
a predetermined mark is present at a predetermined location of the sheet.
In this case, the detecting sensor 123 includes a scanner which reads an
image of the predetermined location and a detector which detects the
predetermined mark from the image read by the scanner. Reuse
determination of the sheets in accordance with the result detected by the
detecting sensor 123 will be described in detail below.

[0056] The transport passage switching mechanism 124 switches a transport
passage used to transport the sheets in accordance with the result
detected by the detecting sensor 123. For example, when the detecting
sensor 123 determines that the sheet is reusable, the transport passage
switching mechanism 124 switches the transport passage to transport the
sheet to the erasing mechanism 125, as indicated by an arrow in FIG. 1.

[0057] Alternatively, when the detecting sensor 123 determines that the
sheet is not reusable, the transport passage switching mechanism 124
switches the transport passage to transport the sheet to the cumulative
unit 11, as indicated an arrow in FIG. 2. In this case, the cumulative
unit 11 cumulates sheets which are not reusable and are to be disposed as
wastes.

[0058] Moreover, the cumulative unit 11 may be equipped with a shredder
which shreds the sheets. In this case, the cumulative unit 11 is
configured to allow the shredder to shred the transported sheets and
collect shredded paper pieces.

[0059] The erasing mechanism 125 erases the image formed on the sheet. For
example, the erasing mechanism 125 heats the sheet up to the erasing
temperature of the ink as the image forming material. In the sheet heated
up to the erasing temperature by the erasing mechanism 125, the image is
erased. The sheet setting mechanism 126 transports and stores the sheet
of which the image is erased by the erasing mechanism 125 to the sheet
cassette 10. Here, the sheet cassette 10 is a cassette which receives the
sheets to be printed by the printer 12A. That is, the image forming
apparatus 1A is capable of reusing the sheets subjected to image reuse
processing by the reuse processing unit 18 as printing sheets.

[0060] Next, operations of the reuse processing unit 18 having the
above-described configuration will be described.

[0061] FIG. 3 is a flowchart explaining an operation example of the reuse
processing unit 18. In addition, the operations of the reuse processing
unit 18 described below are controlled mainly by a controller (not
shown).

[0062] When the sensor (not shown) which is provided in the sheet feeding
tray 16 to detect the sheet detects the sheet (Yes in ACT 11), the pickup
roller 121 inserts each one of the sheets stacked in the sheet feeding
tray 16 into the reuse processing unit 18 (ACT 12). The pair of transport
rollers 122 transports the sheet inserted by the pickup roller 121 to the
detecting sensor 123 (ACT 13). The detecting sensor 123 detects the
information indicating whether the sheet is reusable from the sheet
transported by the pair of transport rollers 122 (ACT 14). For example,
the detecting sensor 123 detects whether the predetermined mark is
present at the predetermined location of the sheet. The reuse
determination of the sheet in accordance with the result detected by the
detecting sensor 123 will be described in detail below.

[0063] When the sheet is determined not to be reusable in accordance with
the reuse determination which is based on the result detected by the
detecting sensor 123 (No in ACT 15), the transport passage switching
mechanism 124 switches the transport passage to transport the sheet to
the cumulative unit 11 (ACT 16), as shown in FIG. 2. The sheet
transported in this manner is cumulated in the cumulative unit 11 (ACT
17).

[0064] Alternatively, when the sheet is determined to be reusable in
accordance with the reuse determination which is based on the result
detected by the detecting sensor 123 (Yes in ACT 15), the transport
passage switching mechanism 124 switches the transport passage to
transport the sheet to the erasing mechanism 125 and the sheet cassette
10 (ACT 18), as shown in FIG. 1. The sheet transported in this manner is
transported to the erasing mechanism 125. The erasing mechanism 125
erases the image formed on the transported sheet (ACT 19). The erasing
mechanism 125 heats the sheet so that the surface of the sheet reaches
the temperature equal to or higher than the erasing temperature in order
to erase the color of the image on the surface of the sheet. The sheet
setting mechanism 126 stores the sheets subjected to the erasing by the
erasing mechanism 125 in the sheet cassette 10 (ACT 20).

[0065] During the series of processing described above, each of the
reusable sheets stacked in the sheet feeding tray is subjected to the
erasing and received in the sheet cassette and each of the non-reusable
sheets stacked in the sheet feeding tray is cumulated in the cumulative
unit 11.

[0066] As described above, the image forming apparatus determines whether
to reuse each one of the sheets stacked in the sheet feeding tray. The
image forming apparatus receives the sheets detected to be reusable as
the printing sheets. The image forming apparatus receives the sheets
detected not to be reusable as wasting sheets. That is, even when the
user stacks the reusable sheets and the non-reusable sheets in the sheet
feeding tray together, the image forming apparatus is capable of
distinguishing the reusable sheets from the non-reusable sheets.
Accordingly, even when the reusable sheets and the non-reusable sheets
coexist, the reusable sheets and the non-reusable sheets can be processed
in the distinguishing manner. For example, even when the user erroneously
places the sheet on which a non-erasable image is printed (the
non-reusable sheet) in the sheet feeding tray, it is possible to surely
cumulate the non-reusable sheet as the wasting sheet in the cumulative
unit.

[0067] Next, an image forming apparatus having a second configuration
example will be described.

[0068] FIGS. 4 and 5 are diagrams illustrating the second configuration
example of the image forming apparatus. An image forming apparatus 1B
shown in FIGS. 4 and 5 is different from the image forming apparatus 1A
having the first configuration example shown in FIGS. 1 and 2 in that the
configuration (image forming method) of a printer 12B is different from
the configuration of the printer 12A. That is, the printer 12A of the
image forming apparatus 1A having the first configuration example shown
in FIGS. 1 and 2 is the ink-jet type printer. However, the printer 12B of
the image forming apparatus 1B having the second configuration example
shown in FIGS. 4 and 5 is an electrophotographic type printer.

[0069] Moreover, in the image forming apparatus 1B having the second
configuration example, the configurations other than the configuration of
the printer 12B may be the same as those in the image forming apparatus
1A having the first configuration example. For example, the configuration
and the operation of a reuse processing unit 18 of the image forming
apparatus 1B are the same as those of the reuse processing unit 18 of the
image forming apparatus 1A. Accordingly, the configuration and the
operation of the reuse processing unit 18 of the image forming apparatus
1B are not described in detail. The image forming apparatus 1B will be
described along with the configuration and the operation of the printer
12B.

[0070] Next, the printer 12B will be described in detail.

[0071] As described above, the printer 12B is the electrophotographic type
printer. Moreover, the printer 12B is also a color printer. The printer
12B includes a sheet feeding roller 102, a pair of transport rollers 103,
a pair of resist rollers 104, a plurality of image forming units 141
(141K, 141C, 141M, and 141Y), an intermediate transfer belt 142, a
driving roller 143, a supporting roller 144, a secondary transfer roller
145, and a fixing unit 146. The image forming unit 141Y (141K, 141C, and
141M) includes an image supporting member Y1 (K1, C1, and M1), a charging
roller Y2 (K2, C2, and M2), an exposure member Y3 (K3, C3, and M3), and a
development member Y4, (K4, C4, and M4), a transfer roller Y5 (K5, C5,
and M5), and a cleaner Y6 (K6, C6, and M6).

[0072] The sheet feeding roller 102 takes out each one of the sheets P
stacked in a sheet cassette 10. The sheet feeding roller 102 transports
the sheet P taken out from the sheet cassette 10 to the pair of transport
rollers 103 and the pair of resist rollers 104. The pair of resist
rollers 104 transports the sheet P at predetermined timing.

[0073] The plurality of image forming units (141K, 141C, 141M, and 141Y)
are respectively arranged opposite the intermediate transfer belt 142
serving as an intermediate transfer member as a transfer-receiving
member. The intermediate transfer belt 142 as the transfer-receiving
member is held with appropriate tension by the driving roller 143 and the
supporting roller 144. The intermediate transfer belt 142 is driven with
the rotation of the driving roller 143. Each of the image forming units
(141K, 141C, 141M, and 141Y) forms a toner image on the intermediate
transfer belt 142 with erasable toner of each color.

[0074] First, in the image forming unit 141Y in a first step, the image
supporting member Y1 is a photoconductive drum which includes a
photoconductive layer such as an organic system or an amorphous silicon
system provided on a conductive base substrate. For example, the
photoconductive drum as the image supporting member is an organic
photoconductive member which charges a negative polarity. The charging
roller Y2 uniformly charges the image supporting member Y1. For example,
the charging roller Y2 uniformly charges the surface of the
photoconductive drum as the image supporting member Y1 with -500 v. The
exposure member Y3 exposes the image supporting member Y1 charged by the
charging roller Y2 using an image-modulated laser beam, an LED or the
like. An electrostatic latent image is formed on the surface of the
photoconductive drum as the image supporting member Y1 exposed by the
exposure member Y3. At this time, the surface potential of the
photoconductive drum as the exposed image supporting member Y1 is about
-80 v, for example.

[0075] The development member Y4 changes the electrostatic latent image
formed on the surface of the photoconductive drum as the image supporting
member Y1 into a visible image. The development member Y4 develops the
electrostatic latent image using a two-component development method in
which nonmagnetic toner charged with a negative polarity and magnetic
carriers are mixed together. That is, the development member Y4 forms
carrier heads on the development roller equipped with a magnet and
applies a potential of -200 to -400 v to the development roller.
Accordingly, on the surface of the photoconductive drum as the image
supporting member Y1, the toner is not attached to a non-exposure member,
but is attached to the exposure member. The toner within the development
member Y4 is erasable yellow toner. Accordingly, the image forming unit
141Y forms a toner image on the surface of the photoconductive drum as
the image supporting member Y1 with the erasable yellow toner supplied by
the development member Y4.

[0076] Moreover, the development method is not limited to the
two-component development method, but a contact one-component development
method, a non-contact one-component development method, a conductive
one-component development method, or the like may be used. The toner
image formed on the surface of the photoconductive drum as the image
supporting member Y1 is transferred to the intermediate transfer belt 142
as the transfer-receiving member. The transfer roller Y5 as the transfer
member comes in contact with the rear surface of the intermediate
transfer belt 142, when viewed from the image supporting member Y1. The
transfer roller Y5 supplies an electric field to be used to transfer the
toner image from the rear surface of the intermediate transfer belt 142.
Voltage applied to the transfer member is in the range of about 300 to 2
kv. The cleaner Y6 removes the toner or the like remaining on the surface
of the photoconductive drum as the image supporting member Y1 after the
transferring. The cleaner Y6 is provided in the front of the charging
roller Y2 in a rotational direction of the photoconductive drum as the
image supporting member Y1. The toner removed from the image supporting
member Y1 by the cleaner Y6 is collected in a void toner box (not shown).

[0077] The image forming units 141M, 141C, and 141K have the same
configuration as that of the image forming unit 141Y described above.
That is, the image supporting member M1 (C1 and K1), the charging roller
M2 (C2 and K2), the exposure member M3 (C3 and K3), the development
member M4 (C4 and K4), and the transfer roller M5 (C5 and K5) have the
same configuration as those of the image supporting member Y1, the
charging roller Y2, the exposure member Y3, the development member Y4,
and the transfer roller Y5, respectively.

[0078] The image forming units repeatedly transfer (primary-transfers) the
toner image developed with the erasable toner of respective colors on the
intermediate transfer belt 142. As a result, a color image in which the
erasable toner image of each color is overlapped with each other is
formed on the intermediate transfer belt 142. The color image formed of
the toner of plural colors transferred on the intermediate transfer belt
142 as the transfer-receiving member is secondary-transferred on the
sheet P at a predetermined secondary transfer location. The support
roller 144 and the secondary transfer roller 145 are provided at the
secondary transfer location where the toner images on the intermediate
transfer belt 142 are transferred on the sheet. In this case, the pair of
resist rollers 104 transports the sheet P to the secondary transfer
location at timing at which the toner images on the intermediate transfer
belt 142 arrive. The toner images on the intermediate transfer belt 142
are transferred to the sheet at the secondary transfer location.

[0079] When the support roller 144 is grounded, a positive (+) polarity
bias is applied to the secondary transfer roller 145 in order to transfer
toner to the sheet P as a second transfer-receiving member. As for a
transfer bias, a value adjusted in accordance with resistance or
environment of the secondary transfer roller 145 and resistance of the
sheet as the second transfer-receiving member is selected. For example,
the transfer bias is selected from a value in the range of +300 to 5 kv.
In addition, by grounding the secondary transfer roller 145, a bias of a
negative polarity may be applied to the support roller 144. The sheet P
to which the toner images are transferred at the secondary transfer
location is discharged to the sheet discharging tray 14 through the
fixing unit 146. The fixing unit 146 fixes the toner images transferred
to the sheet P to the sheet P.

[0080] As described above, the toner images fixed to the sheet by the
fixing unit 146 is formed by the erasable toner of each color.
Accordingly, the colors of the toner images as the color image fixed to
the sheet are erasable. For example, the toner images on the sheet are
erased when the toner images are heated with a temperature equal to or
higher than a predetermined color-erasable temperature (at least a
temperature equal to or higher than a fixing temperature).

[0081] The transfer rollers Y5, M5, C5, and K5 are formed of, for example,
a urethane sponge of which resistance is adjusted. For example, the
transfer rollers Y5, M5, C5, and K5 may be formed of a Φ 14 mm roller
in which a sponge having a 106 Ωcm resistant value is formed in an
Φ 8 mm shaft. As the transfer roller which is the primary transfer
member, a member having certain resistance, such as a transfer brush or a
transfer blade, may be provided. In the intermediate transfer belt 142,
resistance thereof is adjusted by dispersing carbon in polyimide resin
having a 100 μm thickness, for example. The charging rollers Y2, M2,
C2, and K2 are formed by forming urethane rubber around a metal shaft
(Φ 8 mm) and coating nylon resin having a good detachable property on
the surface, for example. In this case, the charging rollers Y2, M2, C2,
and K2 may be configured so that a urethane rubber layer (t=3 mm) has a
resistant value of 2×107 Ωcm and the surface layer (t=0.05
mm) has a resistant value of 5×108 Ωcm.

[0082] In the electrophotographic type printer described above, it is
assumed that the toner as the image forming material erasable
(color-erasable) by heat is used. In this case, it is required that the
temperature equal to or higher than the erasing temperature is not
applied to the toner in printing. That is because when the image forming
material is heated with the temperature equal to or higher than the
erasing temperature before the image forming material is printed on the
sheet, the image forming material may be erased. In this case, it is
preferable that the erasing temperature of the toner is set to be as low
as possible in consideration of the power consumption of the printer.
Accordingly, the temperature applied to the toner is set to be not high
as much as possible within the printer.

[0083] That is, the electrophotographic type printer described above is
designed so that the temperature applied to the toner during the printing
does not reach or exceed the erasing temperature. For example, in the
electrophotographic type printer shown in FIG. 4 or 5, the erasing
temperature of the toner is set to be higher than the fixing temperature
in fixing (which is a process in which a temperature given to the toner
in the printing is the highest). For example, on the assumption that the
fixing temperature is 120°, the erasing temperature of the toner
used in the electrophotographic type printer is set to 140°.

[0084] Moreover, the printer 12B using the erasable toner described above
prints an image on the sheet and also prints information indicating the
reusable sheet. The information indicating the reusable sheet is
information detected by the detecting sensor 123 which will be described
below. For example, the information indicating the reusable sheet is a
mark which is printed on the sheet under a specific condition. In this
case, the printer 12B prints the mark, whenever the printer 12B prints
the image on every sheet. This mark may be printed in advance on the
sheet. At this time, the printer 12B may not print the mark.

[0085] Next, an image forming apparatus having a third configuration
example will be described.

[0086] FIGS. 6 and 7 are diagrams illustrating the third configuration
example of the image forming apparatus. An image forming apparatus 1C
shown in FIGS. 6 and 7 is provided with a reuse sheet cassette receiving
reusable sheets and a new sheet cassette receiving new sheets which are a
cassette receiving sheets. The image forming apparatus 1C having the
third configuration example shown in FIGS. 6 and 7 includes a reusable
sheet cassette 10R and a new sheet cassette 10N in place of the sheet
cassette 10 of the image forming apparatus 1A having the first
configuration example shown in FIGS. 1 and 2. A printer 12C of the image
forming apparatus 1C is capable of carrying out the same functions even
when the printer 12C is replaced with the electrophotographic type
printer 12B shown in FIGS. 4 and 5.

[0087] As shown in FIG. 6 or 7, in the image forming apparatus 1C
including the reusable sheet cassette 10R and the new sheet cassette 10N
as the cassette receiving print sheets, a user is able to select sheets
on which an image is formed, between the reusable sheets and the new
sheets through an operation panel (not shown). For example, in the image
forming apparatus 1C, the user is able to select the reusable sheets upon
printing to correct a document which is being prepared and selects the
new sheets upon printing important data. That is, in the image forming
apparatus 1C, the print sheets are selected in accordance with a request
of the user.

[0088] The printer 12C takes out each one of the sheets from the cassette
in which the sheets selected by the user for the printing are received
(or the cassette selected by the user in person). For example, when the
user selects the reusable sheets, the printer 12C allows a pickup roller
102R to pick up each of the sheets P from the reusable sheet cassette
10R. Each of the sheets P picked up by the pickup roller 102R is
transported to a pair of resist rollers 104 by a pair of transport
rollers 103R or the like. When each of the sheets P is transported to the
pair of resist rollers 104, the printer 12C prints an image on the sheet
P and then discharges the sheet P to a sheet discharging tray 14, as in
the printer 12A of the image forming apparatus 1A.

[0089] When the user selects the new sheets, the printer 12C allows a
pickup roller 102N to pick up each one of new sheets P' from the new
sheet cassette 10N. Each one of the sheets P' picked up by the pickup
roller 102N is transported to the pair of resist rollers 104 by a pair of
transport rollers 103N, the pair of transport rollers 103R, and the like.
When each of the sheets P' is transported to the pair of resist rollers
104, the printer 12C prints an image on the sheet P' and then discharges
the sheet P' to the sheet discharging tray 14, as in the printer 12A of
the image forming apparatus 1A.

[0090] Moreover, the printer 12C using the erasable ink described above
prints the image on the reusable sheet P or the new sheet P' and also
prints the information (mark) indicating the reusable sheet, as in the
printer 12A of the image forming apparatus 1A.

[0091] The configuration and operation of a reuse processing unit 18 of
the image forming apparatus 1C are the same as those of the reuse
processing unit 18 of the image forming apparatus 1A. However, in the
reuse processing unit 18 of the image forming apparatus 1C, a cassette
receiving the sheets subjected to erasing by the erasing mechanism 125 is
the reusable sheet cassette 10R. Accordingly, detailed description of the
configuration and operation of the reuse processing unit 18 of the image
forming apparatus 1C is omitted. The method of selecting the new sheets
or the reusable sheets (or selecting the cassette) is not limited to the
method of directly selecting the sheets through the operation panel (not
shown). For example, the new sheets or the reusable sheets (the cassette)
may be selected by an external apparatus such as a PC on which a printer
driver requesting the image forming apparatus to print the image is
executed.

[0092] Next, an image forming apparatus having a fourth configuration
example will be described.

[0093] FIGS. 8 and 9 are diagrams illustrating the fourth configuration
example of the image forming apparatus. In an image forming apparatus 1D
having the fourth configuration example shown in FIGS. 8 and 9, an
erasing mechanism 151 erasing an image on a sheet is provided within a
printer 12D. The image forming apparatus in shown in FIGS. 8 and 9 is
equipped with a reusable sheet cassette 10R receiving the reusable sheets
and a new sheet cassette 10N receiving new sheets, as in the image
forming apparatus 1C having the third configuration example.

[0094] The image forming apparatus 1D shown in FIGS. 8 and 9 has the same
configuration as that of the image forming apparatus 1C having the third
configuration example, except that the erasing mechanism 151 is not
provided within a reuse processing unit 18B but provided within the
printer 12D. In the image forming apparatus 1D shown in FIGS. 8 and 9,
sheets which are not subjected to the erasing of an image are received in
the reusable sheet cassette 10R. That is, an image on the sheet is not
erased in the reuse processing unit 18B of the image forming apparatus 1D
and the reusable sheets and the non-reusable sheets are distinguished to
be transported to the reusable sheet cassette 10R or the cumulative unit
11. The printer 12D of the image forming apparatus 1D is capable of
carrying out the same functions even when the printer 12D is replaced
with the electrophotographic type printer 12B, which is shown in FIGS. 4
and 5, including the erasing mechanism 151.

[0095] Next, the printer 12D of the image forming apparatus 1D will be
described.

[0096] In the image forming apparatus 1D shown in FIGS. 8 and 9, the user
selects print sheets between the reusable sheets and new sheets, as in
the image forming apparatus 1C having the third configuration example.

[0097] When the user selects the new sheets as the print sheets, the
pickup roller 102N picks up the sheet P' from the new sheet cassette 10N.
The pair of transport rollers 103N and the pair of transport rollers 103R
transport the sheet P' picked up by the pickup roller 102N to the pair of
resist rollers 104 through the erasing mechanism 151. In this case, since
this sheet is the new sheet, the erasing of an image is not necessary.
Accordingly, the erasing mechanism 151 passes the sheet P' being in a
standby state. The pair of resist rollers 104 transports the sheet P' to
the transport belt 107 at predetermined timing. The printer 12D prints an
image on the sheet P' transported through the transport belt 107 and
discharges the sheet P' to the sheet discharging tray 14, as in the
printer 12A.

[0098] Alternatively, when the user selects the reusable sheet as the
print sheet (or does not select the new sheet), the pickup roller 102R
picks up the sheet P from the reusable sheet cassette 10R. The pair of
transport rollers 103R transports the sheet P picked up by the pickup
roller 102R to the erasing mechanism 151. In this case, the reusable
sheet P is not subjected to the erasing of an image. Accordingly, the
erasing mechanism 151 operates in order to erase the image on this sheet.

[0099] That is, the erasing mechanism 151 heats a heat member heating the
sheet up to the temperature equal to or higher than a predetermined
erasing temperature so that the color of the image is erased. At this
time, the erasing mechanism 151 heats the sheet P being transported with
the temperature equal to or higher than the predetermined erasing
temperature. The image on the sheet P which is heated with the
temperature equal to or higher than the predetermined erasing temperature
is erased. The sheet P of which the image is erased by the erasing
mechanism 151 is transported to the pair of resist rollers 104. The pair
of resist rollers 104 transports the sheet P subjected to the erasing to
the transport belt 107 at predetermined timing. The printer 12D prints an
image on the sheet P subjected to the erasing and discharges the sheet P
to the sheet discharging tray 14, as in the printer 12A.

[0100] Next, operations of the printer 12D having the above-described
configuration will be described.

[0101] FIG. 10 is a flowchart explaining an operation example of the
printer 12D. The operations of the printer 12D described below are mainly
controlled by a controller (not shown).

[0102] When the user selects the new sheet as the print sheet (ACT 31, new
sheet), the pickup roller 102N picks up one of the sheets P' from the new
sheet cassette 10N (ACT 32). In this case, the erasing mechanism 151 does
not operate so as not to heat the sheet (ACT 33). In this state, the
sheet P' taken out from the new sheet cassette 10N is transported to the
pair of resist rollers 104. Moreover, the new sheet taken out from the
new sheet cassette 10N may not be passed through the erasing mechanism
151, but may be transported to the pair of resist rollers 104 through a
transport passage.

[0103] Alternatively, when the user selects the reusable sheet as the
print sheet (ACT 31, reuse), the pickup roller 102R picks up one of the
sheets P from the reusable sheet cassette 10R (ACT 34). In this case, the
erasing mechanism 151 becomes a driving state, since the erasing
mechanism 151 heats the sheet P with the temperature equal to or higher
than the predetermined erasing temperature (ACT 35). In this state, the
sheet P taken out from the reusable sheet cassette 10R is passed through
the erasing mechanism 151. The erasing mechanism 151 erases the image on
the sheet P by heating the passing sheet P with the temperature equal to
or higher than the predetermined erasing temperature (ACT 36). The sheet
P of which the image is erased by the erasing mechanism 151 is
transported to the pair of resist rollers 104.

[0104] When the sheet P reaches the pair of resist rollers 104, the pair
of resist rollers 104 transports the sheet P' or the sheet P subjected to
the erasing to the transport belt 107 at predetermined timing. A desired
image is formed on the sheet P' or the sheet P supplied to the transport
belt 107 (ACT 37). At this time, not only the image but also the mark as
the information indicating the reusable sheet are printed on the reusable
sheet P or the new sheet P'. The reusable sheet P or the new sheet P' on
which the image and the mark are printed is discharged to the sheet
discharging tray 14 (ACT 38).

[0105] As the result of the printing described above, the image on the
sheet taken out from the reusable sheet cassette is erased, and then an
image is again printed on the sheet with color erasable ink.

[0106] Next, the reuse processing unit 18B of the image forming apparatus
1D will be described.

[0107] The erasing mechanism 151 is not provided in the reuse processing
unit 18B of the image forming apparatus 1D. Accordingly, the reuse
processing unit 18B executes the process of the reuse processing unit 18
of the image forming apparatus 1A, 1B, or 1C except for the erasing of an
image.

[0108] That is, in the reuse processing unit 18B, the pickup roller 121
picks up each one of the sheets stacked in the sheet feeding tray 16. The
pair of transport rollers 122 transports the sheet picked up by the
pickup roller 121. The detecting sensor 123 determines whether the sheet
transported by the pair of transport rollers 122 is reusable.

[0109] When the detecting sensor 123 determines that the sheet is not
reusable, the transport passage switching mechanism 124 switches the
transport passage, as indicated by an arrow in FIG. 9. In this case, the
sheet is cumulated in the cumulative unit 11. Alternatively, when the
detecting sensor 123 determines the sheet is reusable, the transport
passage switching mechanism 124 switches the transport passage, as
indicated by an arrow in FIG. 8. In this case, the sheet is received in
the reusable sheet cassette 10R. The erasing mechanism erasing an image
on a sheet is not provided in the reuse processing unit 18B. Accordingly,
the reuse processing unit 18B does not erase the image on the reusable
sheet and receives the reusable sheet in the reusable sheet cassette 10R.

[0110] Next, operations of the reuse processing unit 18B having the
above-described configuration will be described.

[0111] FIG. 11 is a flowchart explaining an operation example of the reuse
processing unit 18B. The operations of the reuse processing unit 18B
described below are mainly controlled by the controller (not shown).

[0112] When a sensor (not shown) detecting a sheet detects the sheets
received in the sheet feeding tray 16 (Yes in ACT 41), the pickup roller
121 picks up each one of the sheets on the sheet feeding tray 16 and
inserts the sheet into the reuse processing unit 18B (ACT 42). The pair
of transport rollers 122 transports the sheet picked up by the pickup
roller 121 to the detecting sensor 123 (ACT 43). The detecting sensor 123
detects information indicating whether the sheet transported by the pair
of transport rollers 122 is reusable (ACT 44).

[0113] When it is determined that the sheet is not the reusable sheet in
accordance with the reuse determination which is based on the detection
result of the detecting sensor 123 (No in ACT 45), the transport passage
switching mechanism 124 switches the transport passage to transport the
sheet to the cumulative unit 11, as shown in FIG. 9 (ACT 46). In this
state, the sheet is cumulated in the cumulative unit 11 by the sheet
cumulating mechanism 127 (ACT 47).

[0114] Alternatively, when it is determined that the sheet is the reusable
sheet in accordance with the reuse determination which is based on the
detection result of the detecting sensor 123 (Yes in ACT 45), the
transport passage switching mechanism 124 switches the transport passage
to transport the sheet to the reusable sheet cassette 10R, as shown in
FIG. 8 (ACT 48). In this state, the sheet is received in the reusable
sheet cassette 10R by a transport roller 128 and the sheet setting
mechanism 126 (ACT 49).

[0115] As the result of the processing described above, the reusable
sheets stacked in the sheet feeding tray are received in the reusable
sheet cassette without change (state where the color of the image is not
erased) and the sheets which are stacked in the sheet feeding tray and
not reusable are cumulated in the cumulative unit.

[0116] Next, the reuse determination which is based on the detection
result of the detecting sensor 123 will be described.

[0117] The reuse processing unit 18 of the image forming apparatus 1A, 1B,
or 1C or the reuse processing unit 18B of the image forming apparatus 1D
determines whether the sheet is reusable on the basis of the detection
result of the detecting sensor 123. That is, the detecting sensor 123
detects whether information indicating a possibility of the reuse of the
sheet is present on the sheet. In this embodiment, the detecting sensor
123 is configured to detect a predetermined mark as the information
indicating the possibility of the reuse of the sheet.

[0118] The detecting sensor 123 may be configured to include a scanner
which reads an image of an area containing a location where the mark is
printed on the sheet and a detector which detects the predetermined mark
from the image read by the scanner. Alternatively, the detecting sensor
123 may be configured to include a scanner and a controller (not shown)
may determine whether the mark is present (reuse determination).

[0119] In this case, the mark as the information indicating the
possibility of the reuse of the sheet can be realized in various forms in
accordance with an operation scheme. For example, the mark may be printed
together when a printer of the image forming apparatus prints an image.
Alternatively, the mark may be assigned in advance to the sheet.
Moreover, the mark is not limited to a specific shape or color. A
location where the mark is printed is not limited to a specific location,
as long as the location does not interfere with a main image.

[0120] Here, it is assumed that the mark is printed on the reusable sheet
under a predetermined condition. For example, on the reusable sheet, the
mark having an "R" shape is printed with yellow ink (or toner) at a
location of 5 mm from a front end of the sheet and 10 mm from a right end
of the sheet. In this case, the mark is detected by scanning the area of
5 mm from the front end of the sheet and 10 mm from the right end of the
sheet and determining whether the mark having the yellow "R" shape is
present from a scanned image. It is rare that the mark satisfying the
above-mentioned condition is not intended and is printed by a known
printer. Accordingly, the method of distinguishing the reusable sheets
from the non-reusable sheets by determining whether to detect the
above-mentioned mark can be realized.

[0121] The mark indicating the possibility of the reuse of the sheet is
not limited to a specific color or shape. For example, it is possible to
realize a method of printing the mark having a predetermined shape with
Bk ink (or toner) having a high visibility so that it is easy for a user
to determine the possibility of the reuse. Alternatively, a method of
printing a mark which a user cannot view may be taken into consideration.
In addition, a method of printing a mark on a sheet with special ink or
toner which is not used in a general printer may be taken into
consideration.

[0122] FIG. 12 is a diagram illustrating a configuration example of an
image forming apparatus 1E capable of printing the mark with special ink.
The image forming apparatus 1E having the configuration example shown in
FIG. 12 comprises a printer 12E and a reuse processing unit 18. The
printer 12E includes a recording head 161 as well as four-color ink
heads. The recording head 161 records the mark with the special ink which
is not used in the printing of an image. In this case, the detecting
sensor 123 is configured as a sensor which detects the special ink used
by the recording head 161.

[0123] For example, the recording head 161 prints the mark with the
specific ink capable of being detected by ultraviolet light on a sheet.
In this case, the detecting sensor 123 is configured as a sensor which
detects the mark printed by the recording head 161 by radiating
ultraviolet light onto the sheet.

[0124] Moreover, the recording head 161 may be a unit which prints the
mark with magnetic ink containing particles having a magnetic property.
In this case, the detecting sensor 123 is configured as a magnetic sensor
which detects the magnetism contained in the magnetic ink forming the
mark on the sheet.

[0125] Moreover, the shape of the mark is not limited to the "R" shape,
but may be printed as various shapes such as a triangle, a square, a
diamond shape, a pentagon, a hexagon, a star shape, or a ring shape.
Moreover, the location of the mark is not limited to the front end of the
sheet, but may be in the rear end, the right end, and the left end of the
sheet other than the location of the main image. That is, the mark
indicating the reusability may be appropriately set in accordance with an
operation scheme.

[0126] According to the mode of the printing, an area other than the main
image is very narrow (or not present) in the front end, the rear end, the
right end, and the left end of the sheet in some cases. In this case, it
is difficult to print the mark which can be viewed by a user without the
interference with the main image. In this case, the mark indicating the
possibility of the reuse of the sheet may be printed so that the mark
cannot be viewed by a human. For example, a method of printing the mark
indicating the possibility of the reuse of the sheet with ink invisible
to a human may be taken into consideration. Moreover, the mark indicating
the possibility of the reuse of the sheet may be contained as information
in the main image printed on the sheet by an electronic water marking
technique or the like. In this case, it is necessary for the detecting
sensor 123 to detect the mark which is invisible to a human.

[0127] Next, an erasing mechanism as an image erasing apparatus which
erases a color of an image on a sheet will be described. Here, the
erasing mechanism described below has a configuration which is applicable
to the erasing mechanism 125 or the erasing mechanism 151 in the reuse
processing unit 18, for example.

[0128] Here, the erasing mechanism is configured to erase the color of the
image by applying heat to the sheet. In this case, the erasing mechanism
may be configured with a thermal head, a thermal bar, or a heat roller.
When the heat roller is used, it takes time to increase the temperature
of the heat roller up to a temperature at which the erasing is possible.
For example, when the heat roller is not heated in advance, the sheets
which are received in a tray and to be reused cannot be immediately
subjected to the erasing. For that reason, there is a possibility that
the sheets which need to be erased are stacked in the tray. In the
erasing mechanism using the thermal head or the thermal bar, time
required to increase the temperature thereof is short. However, in a
structure in which the thermal head or the thermal bar is brought into
contact to the surface of a sheet, an erasing performance may
considerably deteriorate, since the image forming material such as ink or
toner is readily attached on the surface of the thermal head or the
thermal bar.

[0129] As the erasing mechanism of the image forming apparatuses 1A, 1B,
1C, and 1D described above, an erasing mechanism 210 or 220 having a
configuration described below may be used.

[0130] FIG. 13 is a diagram illustrating a first configuration example of
the erasing mechanism 210.

[0131] The erasing mechanism 210 shown in FIG. 13 includes a belt 211, a
support roller 212, a support roller 213, an IH heater 215, and a counter
roller 214.

[0132] The belt 211 is suspended on the support rollers 212 and 213. The
belt 211 is driven with the rotation of the support rollers 212 and 213.
The counter roller 214 is opposed to the support roller 212 with the belt
211 interposed therebetween. The sheet P is passed between the counter
roller 214 and the belt 211 supported by the support roller 212.

[0133] The IH heater 215 heats the surface of the belt 211. The IH heater
215 supplies heat to the sheet through the belt 211. That is, the IH
heater 215 may be provided so as to supply heat of the temperature equal
to or higher than the predetermined erasing temperature to the sheet
through the belt 211. For example, the IH heater 215 is disposed opposite
the support roller 213 with the belt 211 interposed therebetween in the
example shown in FIG. 13.

[0134] With the above-described configuration, the erasing mechanism 210
applies the heat of the temperature equal to or higher than the
predetermined erasing temperature to the sheet (the toner or ink on the
surface of the sheet) which is passed between the counter roller 214 and
the belt 211. Colors of the ink or toner as the image forming material
which form an image are erased on the sheet to which the heat of the
temperature equal to or higher than the predetermined erasing temperature
applied to the erasing mechanism 210 is delivered.

[0135] Next, the configuration of the belt 211 used for the erasing
mechanism 210 will be described.

[0136] In the erasing mechanism 210 having the above-described
configuration, the belt 211 has a function of applying the heat supplied
from the IH heater 215 to the sheet. Accordingly, the belt 211 needs to
have a function of holding the heat supplied from the IH heater 215 until
the heat is applied to the sheet and a function of efficiently applying
the held heat to the sheet.

[0137] FIG. 14 is a diagram illustrating a configuration example of the
belt 211. In the example shown in FIG. 14, the belt 211 has a
three-layered structure. As shown in FIG. 14, the belt 211 includes a
base layer 211a, a surface layer 211b, and an intermediate layer 211c.
The base layer 211a is configured as an endless belt of which a base
material is polyimide or the like. The thickness of the base layer 211a
is 75 μm, for example.

[0138] The surface layer 211b is a layer which is directly brought into
contact with the surface of the sheet. It is preferable that the surface
layer 211b has a configuration in which the toner or ink as the image
forming material to be heated is not attached. For example, when the
image forming material is attached to the surface layer 211b, there is a
possibility that the erasing performance deteriorate. In addition, when
the image forming material attached onto the surface layer 211b is
re-attached to the sheet, there is a possibility that the re-attached
image forming material becomes a noise image on the sheet. For that
reason, the surface layer 211b is formed of a Teflon base material, a
silicon base material, or the like having a good detachable property. The
erasing mechanism 210 may include a cleaning mechanism (not shown) which
cleans the surface layer 211b of the belt 211.

[0139] The intermediate layer 211c is used to obtain an insulation effect
between the base layer 211a and the surface layer 211b. Accordingly, the
intermediate layer 211c has a thermal conductivity lower than that of the
surface layer 211b. In the erasing mechanism 210 having the configuration
shown in FIG. 13, a location where the IH heater 215 as a heating source
heats the belt 211 and a location where the belt 211 heats the sheet P
are different from each other. Accordingly, the intermediate 211c holds
the heat supplied from the IH heater 215 to the location where the sheet
P is heated.

[0140] The erasing mechanism 210 described above has a configuration in
which inconvenience caused due to the attachment of the image forming
material such as toner or ink rarely occurs. In the erasing mechanism
210, standby time necessary to be increased up to the erasing temperature
is not required. In this way, the erasing mechanism 210 is capable of
realizing good erasing. The erasing mechanism 210 is a mechanism which
heats the belt 211 using the IH heater 215 as the heating source. This
erasing mechanism 210 is capable of repeating the good erasing with lower
consumption power and without damage to the erasing performance which is
caused due to smear of the image forming material (toner or ink).

[0141] FIG. 15 is a diagram illustrating a second configuration example of
the erasing mechanism 220.

[0142] The erasing mechanism 220 shown in FIG. 15 includes a belt 221, a
support roller 222, a support roller 223, a counter roller 224, and a
heating head 225.

[0143] The belt 221 is suspended on the support roller 222, the support
roller 223, and the heating head 225. The belt 221 is driven with the
rotation of the support rollers 222 and 223. The counter roller 224 is
opposed to the heating head 225 as a heating source with the belt 221
interposed therebetween. The heating head 225 presses the belt 221
against the counter roller 224.

[0144] The sheet P is passed between the counter roller 224 and the belt
211 supported by the heating head 225. The heating head 225 is formed of
a thermal head or a thermal bar. The heating head 225 supplies heat of a
temperature equal to or higher than the erasing temperature of the image
forming material to the sheet P through the belt 221. That is, the
heating head 225 heats the sheet P while pressing the belt 221 against
the sheet P.

[0145] Next, the configuration of the belt 221 used for the erasing
mechanism 220 will be described.

[0146] FIG. 16 is a diagram illustrating a configuration example of the
belt 221. In the example shown in FIG. 16, the belt 221 has a two-layered
structure.

[0147] The belt 221 shown in FIG. 16 includes a base layer 221a and a
surface layer 221b. In the erasing mechanism 220 having the above
described configuration, the belt 221 does not need to hold heat.
Accordingly, the belt 221 does not have the intermediate layer of the
belt 211 described above. It is preferable that the belt 221 possibly
delivers the heat supplied from the heating head 225 to the sheet P
without heat loss. Accordingly, it is preferable that the thickness of
the belt 221 is as thin as possible. However, when the thickness of the
belt 221 is too thin, the strength of the belt may be weak. When the
strength is weak, a life span of the erasing mechanism 220 (the belt 221)
may be shortened. For that reason, it is preferable that the belt 221 is
configured to efficiently conduct the heat while maintaining the strength
in which a predetermined life span is obtained.

[0148] The base layer 221a is formed of a polyimide base material, a metal
material (Ni, SuS, etc.), or the like. The thickness of the base layer
221a is in the range of 20 to 150 μm, for example. The life span of
the belt 221 is also associated with the Young's modulus of a material of
the base layer 221a. In consideration of this point, the base layer 221a
is formed of a polyimide base belt or a metal belt (Ni, SuS, etc.) having
a high Young's modulus.

[0149] The surface layer 221b is a layer which is directly brought into
contact with the surface of the sheet. It is preferable that the surface
layer 221b has a configuration in which toner or ink as the image forming
material to be heated is not attached. For example, when the image
forming material is attached to the surface layer 221b, there is a
possibility that the erasing performance deteriorates. In addition, when
the image forming material attached onto the surface layer 221b is
re-attached to the sheet, there is a possibility that the re-attached
image forming material becomes a noise image on the sheet. For that
reason, the surface layer 221b is formed of a teflon base material, a
silicon base material, or the like having a good detachable property. The
erasing mechanism 220 may include a cleaning mechanism (not shown) which
cleans the surface layer 221b of the belt 221.

[0150] As described above, the erasing mechanism 220 directly applies the
heat to the sheet P while protecting the surface of the sheet with the
belt. In the erasing mechanism 220 having this configuration, standby
time necessary to be increased up to the erasing temperature is not
required. In addition, in the erasing mechanism 220, inconvenience caused
due to the attachment of the image forming material rarely occurs.

[0151] Accordingly, the erasing mechanism 220 is capable of realizing good
erasing. That is, the erasing mechanism 220 is a mechanism which heats
the belt using the thermal bar or the thermal head from the rear surface
of the belt. This erasing mechanism 220 is capable of repeating the good
erasing with lower consumption power and without damage to the erasing
performance which is caused due to smear of the image forming material
(toner or ink).

[0152] The erasing mechanisms 210 and 220 having the configurations shown
in FIGS. 13 and 15, respectively, are similar with the fixing unit used
for the electrophotographic type printer. However, in the fixing unit of
the electrophotographic type printer, it is necessary to control in
accordance with the kind of sheets to be supplied or the number of sheets
to be continuously supplied so that the temperature of the fixing member
reaches a predetermined temperature range without variation in the
temperature of the fixing member. For example, when the fixing
temperature is lower than the predetermined temperature range, low
temperature offset occurs due to the lack of the fixing. Alternatively,
when the fixing temperature is higher than the predetermined temperature
range, high temperature offset occurs due to excessively melted toner.
For example, when sheets having a small size are continuously supplied,
the temperature of both end portions in which the sheets do not pass
increases. When this phenomenon is not appropriately controlled, the high
temperature offset occurs. That is, in the fixing unit, various measures
are necessary in order to strictly control the temperature.

[0153] In the erasing mechanisms 210 and 220 shown in FIGS. 13 and 15,
respectively, the sheets may be heated with the temperature equal to or
higher than the erasing temperature within a range in which damage to the
sheets is not caused. In the erasing mechanisms 210 and 220, the strict
temperature control is not necessary. Accordingly, the erasing mechanisms
210 and 220 having the configurations shown in FIGS. 13 and 15,
respectively, can be realized using a simple temperature control
mechanism and easily realized at low cost.

[0154] Additional advantages and modifications will readily occur to those
skilled in the art. Therefore, the invention in its broader aspects is
not limited to the specific details and representative embodiments shown
and described herein. Accordingly, various modifications may be made
without departing from the spirit or scope of the general inventive
concept as defined by the appended claims and their equivalents.